UV curable ink containing aluminum trihydroxide for use in pad printing, and method of printing

ABSTRACT

Disclosed herein is a game ball, such as a golf ball, having an indicia formed from a UV curable ink containing aluminum trihydroxide (ATH) filler. The ATH improves pad transfer of the ink. An ink composition suitable for pad printing, and a method for applying an indicia to a game ball also are disclosed. The UV curable ink has excellent pad transfer properties, and good durability.

RELATED APPLICATIONS

This application is a continuation of copending application Ser. No.09/233,614, filed Jan. 19, 1999now U.S. Pat. No. 6,191,185, which is adivisional of U.S. application Ser. No. 08/877,938 filed Jun. 18, 1997,now U.S. Pat. No. 5,885,173, which is a continuation-in-part of U.S.application Ser. No. 08/529,361 filed on Sep. 18, 1995, now U.S. Pat.No. 5,770,325, and U.S. application Ser. No. 08/753,704 filed on Nov.27, 1996, now U.S. Pat. No. 5,827,134.

BACKGROUND OF THE INVENTION

The present invention generally relates to inks, and more particularlyto UV curable inks.

UV curable inks are quick-curing inks and therefore are advantageous foruse in continuous-type processes in which subsequent treatment of anink-printed substrate is involved. A number of UV curable inks areknown. For example, U.S. Pat. No. 4,271,258 discloses aphotopolymerizable ink composition containing acrylate resin,methacrylate monomer or oligomer, acrylate monomer or oligomer,photoinitiator, and a particular type of an epoxy resin. U.S. Pat. No.5,391,685 discloses a UV curable ink having an isocyanate compound addedthereto. U.S. Pat. No. 5,391,685 contends that the ink disclosed thereinis particularly well suited for printing on slightly adhesive plasticbases, such as those made of polyoxymethylenes and polypropylenes.

Screen printing on spherical surfaces such as golf balls can bedifficult. As a result, pad printing customarily is used for markinggolf ball surfaces. However, many of the known UV curable inks are notwell suited for pad printing due to difficulties in transferring the inkfrom a pad to a substrate. Furthermore, UV curable inks that can be padprinted have not been found suitable for use on golf balls. Morespecifically, when applied to a golf ball, these inks are notsufficiently durable (impact resistant) to withstand multiple blows by agolf club.

It would be useful to obtain a highly durable UV curable ink which hasfavorable pad transfer properties when used for printing indicia onsurfaces such as a curved and dimpled surface of a golf ball, and whichprovides an image having good durability.

SUMMARY OF THE INVENTION

An object of the invention is to provide a new and improved UV curableink.

Another object of the invention is to provide a UV curable ink which isparticularly well suited for application by pad transfer.

A further object of the invention is to provide a quick curing ink foruse on a game ball, such as a golf ball, and on hard surfaces of othersporting goods, thereby enabling more rapid production.

Another object of the invention is to provide a pad printable, UVcurable ink having good impact resistance.

Yet another object of the invention is to provide a game ball, such as agolf ball, having a clear and durable ink image printed thereon.

A further object of the invention is to provide a method for padprinting an indicia on a hard surface of a game ball, golf club, bat orracket, the indicia comprising a UV curable ink.

Yet another object of the invention is to provide a method for applyinga smudge resistant and durable indicia to a visible surface of a gameball.

Other objects of the invention will be in part obvious and in partpointed out more in detail hereafter.

The invention in a preferred form is a game ball with a surface and anindicia comprising a UV curable ink adhered to the surface, the UVcurable ink containing aluminum trihydroxide. The impact resistance ofthe ink and the adhesion between the indicia and the surface aresufficient to render the game ball suitable for use in competitive play.

The indicia can be applied directly to the cover of a one-piece,two-piece or multi-piece game ball. Alternatively, one or more primercoats can be positioned between the game ball cover and indicia.Furthermore, one or more top coats are positioned over the indicia. Theindicia is sufficiently durable that after the game ball is subjected tothe wet barrel durability test procedure described below, at least about50%, preferably at least about 70%, and more preferably at least about80% of the surface area of the original image remains on the game ball.

Another preferred form of the invention is a UV curable ink composition.The ink composition comprises a UV curable resin, aluminum trihydroxidein an amount appropriate to provide the ink composition with improvedpad transfer, a coloring agent, such as a pigment or dye, and aphotoinitiator for initiating polymerization of the UV curable resin.The ink composition forms a cured indicia having adhesive properties andimpact resistance which render the cured indicia suitable for use ongame balls to be used in competitive play. A thinning agent whichincludes a monomer and/or solvent also is preferably included. A wettingagent and/or extender pigment also can be added. To facilitate padtransfer, the ink has a viscosity of 1,000-28,000 centipoise, preferably1,000-4,000 centipoise, and more preferably 1,000-2,000 centipoise atthe time of application.

Yet another preferred form of the invention is a method of applying anindicia to a game ball. The method comprises the steps of (a) obtaininga UV curable ink composition containing a coloring agent, such as apigment or dye, aluminum trihydroxide, a photoinitiator, and a UVcurable resin, the ink composition having a viscosity of 1,000-28,000and preferably 1,000-4,000 centipoise, (b) applying the ink compositionto the game ball in the form of the indicia, (c) curing the inkcomposition to form a cured film, and (d) applying a coating over theink. The indicia has an impact resistance sufficient to render the gameball suitable for use in competitive play. The ink preferably is appliedby pad printing. The step of UV curing preferably includes placing theindicia under a UV lamp at conditions of lamp intensity, lamp distanceand time sufficient to commence curing of the ink. Curing preferably issubstantially complete within about 1 second. The fully cured inkpreferably, but not necessarily, has a sward hardness (ASTM-D 21 34-66)of 14-40.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and thearticle possessing the features, properties, and the relation ofelements exemplified in the following detailed disclosure.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a game ball having an indicia comprising a UV curable inkin accordance with the present invention.

FIG. 2 schematically shows the durability test apparatus to determinethe durability of the indicia of the invention on a golf ball.

FIG. 3 is a partial side view of a portion of an insert plate in thedurability test apparatus which has grooves intended to simulate a golfclub face.

FIG. 4 shows the differences in pad transfer of four UV curable inks.

DETAILED DESCRIPTION OF THE INVENTION

The UV curable ink of the present invention is unique in that itexhibits a combination of favorable transfer properties and gooddurability or impact resistance. The ink can be used for printingindicia on golf balls, softballs, baseballs, other game balls, as wellas other sporting goods, including but not limited to softball andbaseball bats, tennis and raquetball rackets, and golf clubs. The inkalso can be applied to a variety of materials, including but not limitedto ionomers, polybutadiene, composite materials, metals, etc.

As indicated above, the ink comprises a UV curable resin, a coloringagent, such as a pigment or dye, aluminum trihydroxide, and aphotoinitiator. A thinning agent which includes a monomer and/or asolvent can be added. If necessary, a wetting agent also can beincluded.

The UV curable resin preferably comprises an oligomer. Non-limitingexamples of the oligomer include one or more epoxies, acrylics,acrylated urethanes, elastomeric acrylates, unsaturated polyesters, andpolyethers. Specific examples of suitable oligomers includemethacrylates such as bisphenol A ethoxylate dimethacrylate andacrylated epoxies. Blends of different oligomers can be used. Theoligomer must provide the ink with characteristics of flexibility andimpact resistance that are sufficient to withstand the conditions towhich the substrate is to be subjected. For example, if the substrate isa golf ball, the oligomer must impart to the ink more flexibility thanis inherent in the underlying substrate if optimum durability isdesired. When a top coat is to be placed over the ink, the ink shouldnot be so highly cross-linked that adhesion of the top coat to the inkis substantially hindered.

The uncured ink preferably comprises about 10-90wt % oligomer, morepreferably about 20-80wt % oligomer, and most preferably about 50-70wt %oligomer.

The coloring agent can be any type of pigment, dye or the like whichwill withstand UV treatment, i.e., which is not UV labile. Furthermore,the coloring agent should permit sufficient passage of UV light throughthe ink by any combination of transmission, reflection, or refractionmechanisms, to initiate photocrosslinking. Liquids or powders can beused. One preferred form of the ink is a powder which is dispersed inliquid monomer. Carbon black and iron oxide black are non-limitingexamples of suitable pigments for making black inks. Red lake andquinacrydones are non-limiting examples of suitable pigments for makingred inks. Blends of different pigments and/or dyes can be used. Theuncured ink preferably contains about 2-60wt % pigment, more preferablyabout 5-30wt % pigment, and most preferably about 5-10 wt % pigment.

The photoinitiator is selected to respond to the wavelength of UVradiation to be used for photoinitiation. It is also important toconsider the color of the ink in selecting the photoinitiator because,as indicated above, it is necessary for the UV light to penetrate theink composition to initiate the cure. More specifically, penetration isrequired in order to cure the portion of the ink which is beneath thesurface. Penetration typically is most difficult when black or whitepigments are used. Non-limiting examples of photoinitiators to be usedin conjunction with black pigment include sulfur-type photoinitiatorssuch as isopropyl thioxanthone, and benzophenone and its derivativesincluding acetophenone types and thioxanthones. Photoactivators can beused in conjunction with one or more photoinitiators. Non-limitingexamples of suitable photoactivators are amine-type photoactivators suchas ethyl 4-dimethylamino benzoate. The uncured ink preferably containsabout 0.3-5wt % photoinitiator, more preferably about 1-4 wt %photoinitiator, and most preferably about 3-4 wt % photoinitiator.Blends of different photoinitiators, or photoinitiators andphotoactivators, can be used.

A thinning agent is added if it is needed to lower the viscosity of theuncured ink composition or to contribute to impact resistance orflexibility. When monomer is used as a thinning agent, it should be aphotopolymerizable monomer which forms a polymeric structure uponirradiation. In contrast, when solvents are used as thinning agents,they evaporate during curing. The monomer can be a monofunctional,difunctional or multifunctional acrylate. Non-limiting examples ofsuitable monomers include 1,6 hexane dioldiacrylate, butanedioldiacrylate, trimethylol propane diacrylate, tripropylene glycoldiacrylate and tetraethylene glycol diacrylate.

The uncured ink preferably contains about 10-70 wt % monomer, morepreferably about 10-60 wt % monomer, and most preferably about 10-55 wt% monomer Preferably, the combination of monomer plus oligomerconstitutes about 45-80 wt % of the uncured ink, more preferably about50-80 wt %, and most preferably about 60-80 wt % of the ink.

Non UV curable quick-drying resins which help in ink transfer from thepad to the ball can be added. Non-limiting examples of such resins arevinyl resins, nitrocellulose, acrylic resins, and other quick-drying,film-forming resins. One preferred resin is an acrylic-OH functionalresin made by McWorther, Inc. of Carpentersville, Ill., sold as Resin975. Typically, if such resins are used, they are added in an amount upto about 30 parts by weight based upon 100 total parts by weight ofuncured ink composition.

When a solvent is used, it typically is a liquid with a fast to moderateevaporation rate which, upon partial evaporation causes the ink to betacky, and thereby promotes transfer onto and off an ink pad. Solventalso can be the medium in which photoinitiator is dissolved. Nonlimiting examples of suitable solvents include aromatic solvents such astoluene, xylene, and ester types such as butyl acetate. The uncured inkpreferably includes about 1-30 wt % solvent, more preferably about 5-20wt % solvent, and most preferably about 8-10 wt % solvent.

Wetting agents can be added if necessary to prevent beading of the inkupon application to the golf ball. Suitable wetting agents include, butare not limited to, silicon surfactants and fluorocarbon surfactants.The uncured ink preferably includes about 0-2 wt % wetting agent. Otheradditives that do not adversely affect the pad transfer and impactresistance of the ink also can be incorporated into the ink composition.

Extender pigments such as talc, barium sulfate and the like can be addedas long as sufficient durability is maintained. Such materials may beused to improve transferability. Typically, if such materials are used,they constitute about 10-40 wt %, or more preferably 20-30 wt %, of theuncured ink formulation.

It has been found that by replacing part or all of the extender pigmentssuch as talc and barium sulfate with aluminum trihydroxide (Al₃O₃(H₂O)₃)(ATH) filler, a number of significant improvements to the UV ink willresult with respect to printing, curing and processing. Additionally,the inclusion of ATH will have minimal effect on the color of the ink.Furthermore, ATH has low oil absorption, thus ink viscosity is increasedvery little. When up to 50 wt % ATH based upon the total (uncured)weight of ink is added, ink transfer from a pad to a substrate isimproved. Significantly, ATH does not absorb UV light so curing of theink is not impeded.

When ATH is used in a UV curable game ball ink, it generally is includedin an amount of 10-50 wt % based upon the total weight of the ink priorto curing. Preferably, ATH is employed in an amount of 10-32 wt %, andmore preferably 20-30 wt %. It is believed that ATH loadings up to atleast 50 wt % based upon the weight of (uncured) ink may be useful foroverall balance of properties. Greater quantities of ATH can be usedwhen a low cost ink is desired and durability requirements are notstringent. Lower quantities of ATH are useful when higher durability isneeded. The ATH preferably is used in a quantity appropriate to impartto the ink a balance of properties such as pad transfer and durabilityof the ink. The ATH used may, for example, have a narrow particle sizedistribution with a median particle size of about 1 micron. However, themedial particle size can be in the range of at least as small as 0.25micron to at least as large as 50 microns.

If ATH is used in combination with talc, barium sulfite, or the like,the ratio of ATH to talc, etc., is preferably about 1:1.

The use of ATH does not impede the curing process. The surface tensionof the ink affects wettability of the substrate. The surface tension ofthe ink should not be substantially higher than the surface tension ofthe substrate upon which it is printed. The viscosity of the ink willdetermine the thickness of the indicia on the cover. If the indicia istoo thick, the UV radiation will not penetrate the indicia and completecuring may become difficult. On the other hand, if the indicia is toothin, the durability of the ink layer may be insufficient for conditionsof play. The indicia has a thickness of less than 100 microns,preferably about 10-40 microns, more preferably 13-30 microns, and mostpreferably 20-25 microns.

The cured ink should be sufficiently flexible that it exhibits goodimpact resistance. It is advantageous for the top coat which is appliedover the ink to react with the ink to hold the ink in place, or to haveadhesion by hydrogen bonding and/or Van Der Waals forces. As anon-limiting example, the ink can be used in conjunction with a twocomponent polyurethane top coat, such as a top coat based on polyesteror acrylic polyols and aliphatic isocyanates such as hexamethylenediisocyanate or isophorone diisocyanate trimers.

It is essential for a top coat to be applied over the indicia to protectthe indicia unless the indicia has sufficient adhesion to the surface towhich it is applied, e.g., the cover or a primer layer, to render theuse of a top coat unnecessary. The adhesion between the ink and the topcoat and/or substrate should be sufficiently strong that the indiciaremains substantially intact when the game ball is used. Standards forimage retention vary depending upon the intended use of the game balland the degree and frequency of impact that the image is required towithstand. When applied to a golf ball, the ink durability should besufficient in order that after the ball is subjected to the wet barreldurability test procedure described below, at least 50% of the surfacearea of the original image remains, more preferably at least 70%, andmost preferably at least 80%.

A UV curable ink formulation of the invention which is used for markinggolf balls is prepared and used in the following way. The photoinitiatoris dissolved in the thinning agent, which is then mixed with oligomer,pigment and aluminum trihydroxide. The mixture is placed in an open orclosed cup dispenser of a pad printing device. A primed but unfinishedgolf ball is obtained. The ball 8, which is shown in finished form inFIG. 1, includes, for example, a core 10, and a durable cover layer 12having a dimpled surface. Alternatively, the core and cover can beformed in one piece. An indicia 14 formed from the UV curable ink is padprinted over the golf ball cover 12. The ink indicia can either bestamped directly on the cover or can be stamped on a primer coat whichis placed over the cover. The unfinished golf ball is then subjected toUV treatment under conditions sufficient to commence curing of the ink.After photoinitiation, curing of the ink is substantially completewithin a time period of between less than one second and a few seconds.

A top coat layer 16 is placed over the ink indicia after the ink iscured. The top coat layer 16 assists in keeping the indicia on the golfball surface, as indicated above, and therefore the adhesion of indiciato the golf ball does not need to be as strong as would be required ifthe ink were to constitute the outer layer of the ball. The top coattypically has a thickness of 10-40 microns.

The conditions of UV exposure which are appropriate to cure the ink canbe ascertained by one having ordinary skill in the art. For example, ithas been found that when a golf ball passes through a UV treatmentapparatus at a rate of 10 ft/min. at a distance of about 1¼-1¾ inchesfrom a UV light source which has an intensity of e.g. 200-300 watts/in²,the indicia should be exposed to UV radiation for no more than a fewseconds, preferably, no more than about 1 second, and more preferably nomore than about 0.7 seconds. Higher and lower UV lamp intensities may beused as long as the cured ink meets the applicable durabilityrequirements. Excess UV exposure is avoided in order to preventdegradation of the substrate. The ink is UV cured prior to applicationof any top coat.

The pad to be used for transfer of the UV ink preferably containssilicone. This type of pad has good elasticity, durability and softnessand an appropriate surface tension. Other types of pads also can beused.

The ink can be applied on a non-UV-labile surface of a game ball.According to the invention, it is generally not necessary to pretreatthe surface prior to application of the ink. If it is desired to applythe UV curable ink on an extremely smooth surface upon which transfer ispoor, the portion of the surface to be stamped can be chemically orphysically etched or abraded in order to provide an ink-receptivesurface.

The ink of the invention has a sward hardness (ASTM-D 2134-66) aftercuring of no more than 55, more preferably no more than 40, and mostpreferably no more than about 20. The UV curable ink of the inventionprovides for durability sufficient to meet stringent durabilitystandards required for commercial grade golf balls. The durability ofthe ink can be determined by testing stamped golf balls in a variety ofways, including using the wet barrel durability test procedure.

Durability according to the wet barrel durability test procedure isdetermined by firing a golf ball at 135 ft/sec (at 72° F.) into 5-sidedsteel pentagonal container, the walls of which are steel plates. Thecontainer 110, which is shown schematically in FIG. 2, has a 19½ inchlong insert plate 112 mounted therein, the central portion 114 of whichhas horizontally extending square grooves on it which are intended tosimulate a square grooved face of a golf club. The grooves, which areshown in an exaggerated form in FIG. 3, have a width 130 of 0.033inches, a depth 132 of 0.100 inches, and are spaced apart from oneanother by land areas 134 having a width of 0.130 inches. The five walls116 of the pentagonal container each have a length of 14½ inches. Theinlet wall is vertical and the insert plate is mounted such that itinclines upward 60° relative to a horizontal plane away from opening 120in container 110. The ball travels 15½-15¾ inches horizontally from itspoint of entry into the container 110 until it hits the square-groovedcentral portion 114 of insert plate 112. The angle between the line oftrajectory of the ball and the insert plate 112 is 30°. The balls aresubjected to 70 or more blows (firings) and are inspected at regularintervals for breakage (i.e., any signs of cover cracking ordelamination). If a microcrack forms in a ball, its speed will changeand the operator is alerted. The operator then visually inspects theball. If the microcrack cannot yet be observed, the ball is returned tothe test until a crack can be visually detected. The balls are thenexamined for adhesion of the ink.

Having generally described the invention, the following examples areincluded for purposes of illustration so that the invention may be morereadily understood and are in no way intended to limit the scope of theinvention unless otherwise specifically indicated.

EXAMPLE 1

A golf ball printing ink was prepared which contains:

5 parts by weight 1,6 hexane dioldiacrylate (sold by Sartomer, Exton,Pa. 19341),

17.5 parts by weight black pigment paste in diacrylate monomer, sold asCarbon Black UV Dispersion 99B415 (Penn Color, Doylestown, Pa.),

35 parts by weight of an aliphatic urethane acrylate oligomer (CN965,sold by Sartomer, Exton, Pa. 19341).

0.5 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

1 part by weight ethyl 4-dimethylamino benzoate, C₁₁H₁₅NO₂, anamine-type photoactivator (EDB, distributed by Aceto Chemical, LakeSuccess, N.Y.),

4.4 parts by weight xylene solvent, and

4.4 parts by butyl acetate solvent.

The photoinitiator and photoactivator were dissolved in the xylene/butylacetate solvent blend. The ink was pad printed using a silicone pad onunprimed, dimpled ionomeric covers of several dozen golf balls. The inkhad a viscosity of about 27,500 (centipoise) cps at the time ofapplication. The balls containing the stamped indicia were passedthrough a Uvex UV treatment apparatus Lab Model #14201 at a rate of 10feet/min, using a lamp intensity of 235 watt/in² and wavelength range of200-400 nm with the indicia being located about 1¾ inches from the UVlight source. The ink was cured in less than about 1 second and had asward hardness of about 14 after curing was complete. The golf ballswere then coated with a solvent borne polyurethane top coat formed froma polyester type hexamethylene diisocyanate. The adhesion of the indiciaon the balls was tested for durability according to the wet barreldurability test procedure described above. After wet barrel durabilitytesting, the balls were examined and it was found that no more thanabout 20% of the surface area of the original ink logo was removed.

EXAMPLE 2

The procedure of Example 1 was repeated with the exception that the inkformulation that was used contained:

10 parts by weight 1,6 hexane dioldiacrylate (sold by Sartomer),

35 parts by weight black pigment paste in diacrylate monomer, sold asCarbon Black UV Dispersion 99B415,

70 parts by weight of a difunctional aliphatic urethane acrylateoligomer (Ebecryl 4833 RadCure, Smyrna, Ga.),

1 part by weight isopropyl thioxanthone, C₁₆H₁₄OS (ITX), and

2 parts by weight ethyl 4-dimethylamino benzoate (EDB).

The ink had a viscosity of about 25,000 cps. The ink was cured in about1 second and produced a film having a sward hardness of about 12. Theballs were subjected to the wet barrel durability test procedure. Afterthe wet barrel durability testing, it was found that no more than about20% of the ink logo was removed.

EXAMPLE 3

The procedure of Example 1 was repeated with the exception that theCN965 oligomer was replaced by a difunctional oligomer sold as Ebecryl8402 (Rad-Cure, Smyrna, Ga.). The ink had a viscosity of about 18,000cps. The ink was cured in about 1 second and produced a film having asward hardness of about 14. The ink was found to be as nearly as durableas that of Examples 1 and 2.

EXAMPLE 4

The procedure of Example 1 was repeated with the exception that the inkformulation that was used contained:

7.3 parts by weight 1,6 hexane dioldiacrylate (sold by Sartomer, Exton,Pa. 19341),

19.2 parts by weight black pigment paste in diacrylate monomer, sold asICU 386 (Industrial Color Ink, Joliette, Ill.),

21.0 parts by weight aliphatic polyether urethane oligomer (BR-571,Bomar Specialties Company, Winsted, Conn.),

0.5 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

1 part by weight ethyl 4-dimethylamino benzoate (EDB),

11.4 parts by weight talc (Vantalc 6H, Vanderbilt, Norwalk, Conn.),

22.9 parts by weight barium sulfate (106 Low-Micron White Barytles,Whittaker, Clark & Daniels, Inc., South Plainfield, N.J.),

12.1 parts by weigh butyl acetate solvent, and

4.6 parts by weight propylene glycol monomethyl ether acetate solvent.

The ink was applied directly to ionomeric covers of golf balls, and alsoover ionomeric covers to which a water borne polyurethane primer layerhad been applied prior to application of the ink. The ink was cured inabout 1 second and produced a film having a sward hardness of about 14.The balls were top coated and subjected to the wet barrel durabilitytest procedure. After the wet barrel durability testing, it was foundthat no more than about 20% of the ink logo was removed.

COMPARATIVE EXAMPLE 1

The procedure of Example 1 was repeated with the exception that acommercially available UV curable ink was used, namely Blk #700801(Trans Tech, Carol Stream, Ill.). The ink had a viscosity of about 6,000cps. The ink was cured in about 1 second and produced a film having asward hardness of about 26. After the wet barrel durability test onlythe outline of the logo remained. Most of the ink in the dimples and onthe land areas had been removed. Intercoat adhesion between the ink andtop coat was poor.

COMPARATIVE EXAMPLE 2

The procedure of Example 1 was repeated on several golf balls with theexception that a commercially available UV curable ink was used, namelyL-526-163-B (Qure Tech, Seabrook, N.H.). The ink had a viscosity ofabout 28,500 cps. The ink was cured in about 1 second and produced afilm having a sward hardness of about 20. As a result of the wet barreldurability test, the ink on at least about 60% of the surface area ofthe logo had been removed. It is believed that the ink was too brittleto withstand the conditions of the wet barrel durability test.

EXAMPLE 5

ATH-containing formulation 1, shown below, was prepared:

ATH-Containing Formulation 1 Parts by weight Acrylic-OH functionalresin¹ 540.5 Acetate and aromatic hydrocarbon solvent blend² 189.2 ATH³270.3 1000.0 ¹McWorther Resin 975 (McWorther, Inc., Carpentersville, IL)²Summit Ink Reducer, Summit PT #910527 (Summit Screen Inks, No. KansasCity, MO) Alternatively, a mixture based upon 43.4 parts by weight butylacetate, 28.3 parts by weight xylene and 28.3 parts by weight propyleneglycol monomethyl ether acetate can be used. ³ATH SpaceRite S-3 (ALCOAIndustries, Bauxite, AR)

The ATH-containing formulation 1 was then used to form a golf ball inkwhich contained:

5 parts by weight aliphatic urethane triacrylate (BR-990, BomarSpecialties Co., Winsted, Conn.),

35 parts by weight ATH-containing formulation 1,

5.5 parts by weight trimethylolpropane triacrylate (TMPTA) (SartomerCo., West Chester, Pa.)

5 parts by weight black dispersion in oligomer/monomers (ICU 386,Industrial Color Inc., Joliette, Ill.),

0.3 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

1 part by weight ethyl 4-dimethylamino benzoate, C₁₁H₁₅NO₂, anamine-type photoactivator (EDB, distributed by Aceto Chemical, LakeSuccess, N.Y.), and

10 parts by weight ATH (SpaceRite S-3, ALCOA Industries, Bauxite, Ark.).

All ingredients were mixed and dispersed on high speed mixing equipment.

The ink was pad printed using a silicone pad on unprimed, dimpledionomeric covers of several dozen golf balls. The balls containing thestamped indicia were passed through a Uvex UV lamp at a rate of 10feet/min., using a lamp intensity of 235 watt per inch² and a wavelengthrange of 200-400 nm with the indicia being located about 1¾ inches fromthe UV light source. The ink was cured in less than one second. The golfballs were then coated with a two component polyester/aliphaticpolyisocyanate clear coat. The printability, jetness, detail image, padrelease, and durability of the ink was evaluated and was compared withthree sets of control inks, designated as Control A, Control B, andControl C. The formulations of the Control A and Control B inks areshown below:

Control A

parts by wt. Aliphatic urethane-acrylic oligomer¹ 6.45 Acrylic-OHfunctional resin² 42.96 Acetate and aromatic hydrocarbon 8.85 solventblend³ Talc⁴ 5.59 Barium sulfate⁵ 12.89 Black dispersion inoligomer/monomer⁶ 6.01 TMPTA⁷ 15.18 Isopropyl thioxanthone⁸ 0.69 Ethyl4-dimethylamino benzoate⁹ 1.38 100.00 ¹BR-571 (Bomar Specialties Co.,Winsted, CT) ²McWorther Resin 975 (McWorther, Inc., Carpentersville, IL)³Summit Ink Reducer (Pt# 910527, Summit Screen Inks, No. Kansas City,MO) ⁴Van Talc #6H (Vanderbilt, Norwalk, CT) ⁵Barytes #22 (Whittaker,Clark & Daniels, Inc., South Plainfield, NJ) ⁶ICU 386 (Industrial ColorInc., Joliette, IL) ⁷(Sartomer Co., West Chester, PA) ⁸ITX (distributedby Aceto Chemical, Lake Success, NY) ⁹EDB (distributed by AcetoChemical, Lake Success, NY)

Control B

parts by wt. Epoxy-acrylate oligomer¹ 19.24 Acrylic-OH functional resin²27.70 Acetate and aromatic hydrocarbon 13.84 solvent blend³ Talc⁴ 7.69Barium sulfate⁵ 7.69 Black dispersion in oligomer/monomer⁶ 6.15Polyester-acrylate oligomer⁷ 15.38 Isopropyl thioxanthone⁸ 0.77 Ethyl4-dimethylamino benzoate⁹ 1.54 100.00 ¹Ebecryl 3700 (Rad-Cure, Smyrna,GA) ²McWorther Resin 975 (McWorther, Inc., Carpentersville, IL) ³SummitInk Reducer (Pt# 910527, Summit Screen Inks, No. Kansas City, MO) ⁴VanTalc 6H (Vanderbilt, Norwalk, CT) ⁵Barytes #22 (Whittaker, Clark &Daniels, Inc., South Plainfield, NJ) ⁶ICU 386 (Industrial Color Inc.,Joliette, IL) ⁷Ebecryl 80 (Rad-Cure, Smyrna, GA) ⁸ITX (distributed byAceto Chemical, Lake Success, NY) ⁹EDB (distributed by Aceto Chemical,Lake Success, NY)

Control C was Trans Tech ink # 2P37-2 (Trans Tech, Carol Stream, Ill.).The ratings for the various ink formulations are shown below:

Detail Pad Ink Printability Jetness Image Release Durability Example 51½ 1 1 1½ 1 Control A 2½ 2½ 2 2½ 1 Control B 3 2½-3 2½ 3 2½ Control C1½-2 1 1 1½-2 2½

Ratings were from 1-5 with 1 being ideal and 5 being unacceptable. Allof the balls of Example 5 and the balls of Controls A, B and C werecovered with a one-coat top coating system of 160 mg, the top coatingbeing a two component polyester/aliphatic polyisocyanate clear coat.

The ink of Example 5 had a oligomer/monomer content of 22.608%, anacrylic resin content of 21.508%, a black pigment content of 3.08 wt %,an ATH pigment content of 31.63 wt %, a solvent content of 20.008% andan initiator content of 1.62 wt %. The density the ink was 10.68lbs./gal., the total nonvolatiles content was 80%, and the volatileorganic compounds constituted 2.14 lbs./gal. The viscosity of the inkwas 11,000 centipoise at the time of application. After curing, thesmudge resistance of the ink was tested using methyl ethyl ketonesolvent. No smudging occurred.

It has been found that the solvent content of the ink can besignificantly increased without reducing the quality of theidentification stamp. For example, by further reducing the ink by 30%(by adding solvent), the viscosity of the ink will decrease to about1420 centipoise. An ink with this low viscosity tends to have betterprintability than more viscous inks on certain pad printing machines.

FIG. 4 shows a silicone pad after 12 golf balls have been stamped with aparticular type of ink. FIG. 4-A shows the stamp after stamping with theink of Control A. FIG. 4-B shows the silicone pad after stamping withthe ink of Control B. FIG. 4-C shows th e pad after stamping with theink of Example 5. FIG. 4-D shows the pad after stamping with Control C.As indicated by the resulting stamps, the best transfer, i.e. the leastquantity of ink remaining on the stamp, resulted from the use of the inkof Example 5.

EXAMPLE 6

ATH-containing formulation 2, shown below, was prepared:

ATH-Containing Formulation 2 Parts by weight Acrylic-OH functionalresin¹ 21.84 Propylene glycol monomethyl ether acetate solvent² 4.85ATH³ 20.70 Talc⁴ 19.50 Black dispersion in oligomer/monomer⁵ 9.50 76.39¹McWorther Resin 975, (McWorther, Inc., Carpentersville, IL) ²DowChemcial (and others) ³ATH SpaceRite S-3 (ALCOA Industries, Bauxite, AR)⁴Van Talc #6H (Vanderbilt, Norwalk, CT) ⁵ICU 386 (Industrial Color Inc.,Joliette, IL)

After the formulation was mixed, the following materials were added:

1.31 parts by weight butyl acetate, (Eastman Chemical and others),

6.16 parts by weight Aromatic 100 or HiSol 53, (Ashland Chemicals),

3.08 parts by weight cyclohexanone (Ashland Chemicals),

0.50 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

1 part by weight ethyl 4-dimethylamino benzoate, C₁₁H₁₅NO₂, anamine-type photoactivator (EDB, distributed by Aceto Chemical, LakeSuccess, N.Y.),

5.78 parts by weight aliphatic urethane triacrylate (UV curable resin)(BR-990, Bomar Specialties Co., Winsted, Conn.), and

5.78 parts by weight trimethylolpropane triacrylate (UV curable resin)(TMPTA) (Sartomer Co., West Chester, Pa.).

The total parts by weight were 100. All ingredients were mixed anddispersed using high speed mixing equipment.

The ink was pad printed using a silicone pad on unprimed, dimpledionomeric covers of a large number of golf balls. The golf ballscontaining a stamped indicia were passed through a Uvex UV lamp at arate of 10 feet per minute, using a lamp intensity of 235 watts perinch² and a wave length range of 200-400 nm with the indicia beinglocated at about 1¾ inches from the UV light source. The ink was curedin less than one second. The golf balls were then coated with atwo-component polyester/aliphatic polyisocyanate clear coat and weresubjected to the wet barrel durability test procedure. After the wetbarrel durability testing, it was found that no more than about 20% ofthe ink logo was removed.

EXAMPLE 7

The procedure of Example 6 was repeated with the exception that thequantity of ATH was reduced to 19.20 parts by weight, and theATH-containing formulation (ATH-containing formulation 2) included only0.22 parts by weight of black dispersion in oligomer/monomer¹, andfurther contained 8.16 parts of a first red dispersion inoligomer/monomer² and 2.62 parts of a second red dispersion inoligomer/monomer³. All ingredients were mixed and dispersed on highspeed mixing equipment. The total parts by weight were 100.

¹ICU 386 (Industrial Color Ink, Joliette, Ill.)

²ICU Red Lake C (Industrial Color Ink, Joliette, Ill.)

³ICU Lithol 388 Red (Industrial Color Ink, Joliette, Ill.)

The ink was pad printed using a silicone pad on unprimed, dimpledionomeric covers of a number of golf balls. The golf balls containing astamped indicia were passed through a Uvex UV lamp at a rate of 10 feetper minute, using a lamp intensity of 235 watts per inch² and a wavelength range of 200-400 nm with the indicia being located about 1¾inches from the UV light source. The ink was cured in less than onesecond. The golf balls were then coated with a two-componentpolyester/aliphatic polyisocyanate clear coat and were subjected to thewet barrel durability test procedure. After the wet barrel durabilitytesting, it was found that no more than about 20% of the ink logo wasremoved.

EXAMPLE 8

ATH-containing formulation 3, shown below, was prepared:

ATH-Containing Formulation 3 Parts by weight Acrylic-OH functionalresin¹ 30.78 Butyl acetate solvent 4.67 Xylene solvent² 3.04 Propyleneglycol monomethyl ether acetate solvent 3.04 ATH³ 31.66 73.19 ¹McWortherResin 975 (McWorther, Inc., Carpentersville, IL) ²Shell ³ATH SpaceRiteS-3 (ALCOA Industries, Bauxite, AR)

After mixing, the following materials were added:

5.69 parts by weight red dispersion in oligomer/monomer (ICU Red Lake C,Industrial Color Ink, Joliette, Ill.),

1.92 parts by weight red dispersion in oligomer/monomer (ICU LitholRubine, Industrial Color Ink, Joliette, Ill.),

0.47 parts by weight black dispersion in oligomer/monomer (ICU 386,Industrial Color Ink, Joliette, Ill.),

0.49 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

1.14 parts by weight ethyl 4-dimethylamino benzoate, C₁₁H₁₄NO₂, anamine-type photoactivator (EDB, distributed by Aceto Chemical, LakeSuccess, N.Y.),

8.14 parts by weight aliphatic urethane triacrylate (BR-990), BomarSpecialties Co., Winsted, Conn.), and

8.95 parts by weight trimethylolpropane triacrylate (TMPTA) (SartomerCo., West Chester, Pa.).

The total parts by weight were 99.99.

To provide for optimum printing, the viscosity of the ink was reduced to1200 centipoise by adding 15 wt % (based upon the weight of the inkbefore reduction) of a solvent which was made by mixing 43.4 parts byweight butyl acetate, 28.3 parts by weight xylene and 28.3 parts byweight propylene glycol monomethyl ether acetate.

The ink was printed on a number of golf balls. The golf balls were thencoated with a two-component polyester/aliphatic polyisocyanate clearcoat and were subjected to the wet barrel durability test procedure.After the wet barrel durability testing, it was found that no more thanabout 20% of the ink logo was removed. The balls which were initiallyprinted had a crisp image. After time, some ghosting appeared.

EXAMPLE 9

ATH-containing formulation 4, as shown below, was prepared:

ATH-Containing Formulation 4 Parts by Weight Acrylic-OH functionalresin¹ 21.63 Butyl Acetate 7.57 ATH² 21.34 Talc³ 19.35 First reddispersion in oligomer/monomer⁴ 7.04 Second red dispersion inoligomer/monomer⁵ 2.26 Black dispersion in oligomer/monomer⁶ 0.61 Xylenesolvent 3.80 ¹McWorther Resin 975 (McWorther, Inc., Carpentersville, IL)²ATH SpaceRite S-3 (ALCOA Industries, Bauxite, AR) ³Van Talc #6H(Vanderbilt, Norwalk, CT) ⁴ICU Red Lake C, (Industrial Color Ink,Joliette, IL) ⁵ICU Lithol Rubine 388, (Industrial Color Ink, Joliette,IL) ⁶ICU 386 (Industrial Color Ink, Joliette, IL)

After mixing, the following materials were added:

3.80 parts by weight propylene glycol monomethyl ether acetate solvent,

0.38 parts by weight isopropyl thioxanthone, C₁₆H₁₄OS, a sulfur-typephotoinitiator (ITX, distributed by Aceto Chemical, Lake Success, N.Y.),

0.86 parts by weight ethyl 4-dimethylamino benzoate, C₁₁H₁₄NO₂, anamino-type photoinitiator (EDB, distributed by Aceto Chemical, LakeSuccess, N.Y.),

5.69 parts by weight aliphatic urethane triacrylate (BR-990, BomarSpecialties Co., Winsted, Conn.), and

5.69 parts by weight trimethylolpropane triacrylate (TMPTA) (SartomerCo., West Chester, Pa.).

Total parts by weight were 100.02.

The ink was printed on a number of golf balls. The image was very dark.A satisfactory image probably could have been obtained using a lowerlevel of black dispersion. The golf balls were then coated with atwo-component polyester/aliphatic polyisocyanate clear coat and weresubjected to the wet barrel durability test procedure. After the wetbarrel durability testing, it was found that no more than about 20% ofthe ink logo was removed.

As will be apparent to persons skilled in the art, various modificationsand adaptations of the structure above described will become readilyapparent without departure from the spirit and scope of the invention,the scope of which is defined in the appended claims.

What is claimed is:
 1. A UV curable ink composition comprising: a UV curable resin; from 20% to about 50% by weight aluminum trihydroxide, the amount of aluminum trihydroxide being appropriate to provide the ink composition with improved pad transfer; a coloring agent, and a photoinitiator for initiating polymerization of the UV curable resin, wherein the ink composition has a viscosity of about 1,000 to about 4,000 centipoise, the ink composition forming cured indicia having adhesive properties, impact resistance, and visible coloring which render the cured indicia suitable for use on a game ball to be used in competitive play.
 2. A UV curable ink composition according to claim 1, wherein the ink composition has a viscosity of about 1,000 to about 2,000 centipoise.
 3. A UV curable ink composition according to claim 1, wherein the ink composition has a Sward Hardness of no more than 55 when fully cured.
 4. A UV curable ink composition comprising: a UV curable resin; from 20% to about 30% by weight aluminum trihydroxide, the amount of aluminum trihydroxide being appropriate to provide the ink composition with improved pad transfer; a coloring agent, and a photoinitiator for initiating polymerization of the UV curable resin, wherein the ink composition has a viscosity of about 1000 to about 4,000 centipoise, the ink composition forming cured indicia having adhesive properties, impact resistance, and visible coloring which render the cured indicia suitable for use on a golf ball to be used in competitive play.
 5. A UV curable ink composition according to claim 4, wherein the ink composition has a viscosity of about 1,000 to about 2,000 centipoise.
 6. A UV curable ink composition according to claim 4, wherein the ink composition has a Sward Hardness of no more than 55 when fully cured. 